With the development of LED technology, the LED brightness and efficiency continues to improve. The continued development of LED lighting technology in daily life is becoming the mainstream in terms of energy saving and emission reduction and green lighting.
A traditional constant-current LED driver circuit with power factor correction (PFC) function powered by an alternating current can be categorized into two types, namely, isolating type and non-isolating type. The isolating type is further categorized into two types of control structure. One is a two-stage control structure and the other is a single-stage control structure. In comparison with the two-stage control structure, the circuit of the single-stage control structure is relatively simple and cost-saving.
In the isolating type LED driver circuit with single-stage control, a constant-current control signal is generally obtained by optical coupler feedback. The use of optical coupler feedback requires an additional error amplifier at the secondary side. The sampling of the output current also requires the optical coupler for isolation so as to deliver the output current to primary side. Thus, such a circuit requires relatively more components and entails a more complex implementation, resulting in a large size of PCB layout, which is unfavorable to the minimization of the products and may lead to a high cost.